Returns a checkbox tag tailored for accessing a specified attribute
(identified by method) on an object assigned to the template
(identified by object). It’s intended that method
returns an integer and if that integer is above zero, then the checkbox is
checked. Additional options on the input tag can be passed as a hash with
options. The checked_value defaults to 1 while the
default unchecked_value is set to 0 which is convenient for
boolean values. Since HTTP standards say that unchecked checkboxes
don’t post anything, we add a hidden value with the same name as the
checkbox as a work around.

>InthedocsforActionView::Helpers::FormHelper#check_box, when>discussingwhythemethodaddsahiddeninputtag_after_thecheckbox>tag,itsays>>"...Rails parameters extraction always gets the first occurrence of
> any given key...">>I'm not sure this is still the case.
Indeed it changed in 2.3 but unfortunately the patch didn'tupdatethedocs.Wenoticedthisafewdaysago,theyarecorrectnowinedge.